It is desirable to remove particulates and water from air prior to introducing the air into an internal combustion engine. In certain environments, it is advantageous to include a precleaner for removing water and larger sized particulates prior to cleaning the air in an air cleaner. Removing water and larger size particulates from an air stream fed to an air cleaner has a tendency to help prolong the life of the main or primary filter element inside the air cleaner. Precleaners are often provided as part of an air cleaner. Exemplary disclosures of air cleaners containing a precleaner include U.S. Pat. No. 7,008,467, U.S. Pat. No. 6,350,291, European Patent No. EP 1 364 695, and PCT Publication No. WO2007/000397. Because air cleaners for engines are often located in the engine compartment of a motor vehicle, there is limited space for a precleaner.
The engine air intake for motor vehicles used in agricultural and construction industries is commonly located above the hood line of the vehicle to obtain a source of air that is a reasonable distance away from the tool being used (e.g., the tool turning the soil or modifying the earth grade in the example of agricultural or construction equipment). This provides an air source that is lower in dust concentration than the air immediately adjacent to the engine compartment. This location necessitates a duct that is oriented vertically to direct the air in a downward direction toward the hood (if so equipped) and subsequently to the remainder of the engine air intake components. A vertically oriented duct or stack is typically fitted with a raincap to prevent rain and other falling objects from being ingested directly into the vertical duct or stack. A typical raincap is commonly fitted with a cap to deflect rain, and an annular aperture to allow for the introduction of air into the cavity between the cap and the vertical duct or stack. The annular aperture is commonly sized to allow the environmental air to be introduced at a relatively low velocity (typically less than 600 fpm) to allow larger droplets and objects to fall out of the airflow before entering the cavity beyond the annular aperture. The air then turns approximately 180 degrees within the cavity as it enters the vertical duct or stack and is conveyed to the next component of the engine air intake system.
Exemplary precleaners that are referred to as inertial separators or centrifugal separators are manufactured by Donaldson Company Inc and are available under the name Donaldson Strata™ Tubes and Panels. Exemplary inertial separators are disclosed by U.S. Pat. No. 4,242,115 and U.S. Pat. No. 4,746,340.